Method and apparatus for the recovery of waterjet power for marine vessels

ABSTRACT

The method of improving the net thrust minus drag of a marine vessel at a given engine performance by creating a secondary jet flow consisting of (1) a portion of the primary jet water, (2) ambient water induced by the primary jet water, and (3) ambient water captured by the ram action when forward motion is achieved by the vessel. The apparatus includes a duct having an inlet means located at a certain distance aft of the primary jet and an outlet with nozzle means to augment in producing the secondary jet.

United States Patent 1 1 111*] 3,763,818 Davis Oct. 9, 1973 {54] METHOD AND APPARATUS FOR THE 111,899 12/1928 Austria 115/ 14 RECOVERY OF WATERJET POWER FOR 287,510 10/1928 Great Britain 115/1 1 The Boeing Company, Seattle, Wash.

Filed: Mar. 20, 1972 Appl. No.2 235,895

Inventor: Assignee:

Primary Examiner-Robert S. Ward, Jr. Attorney-Kenneth W. Thomas et al.

[5 7] ABSTRACT The method of improving the net thrust minus drag of y [52] US. Cl. 115/11, 60/222 3 marine Vessel at a given engine Performance y 51 1111.0 B63h 11/02 s seconda'ry jet flow consisting of a portion 58 Field 61 Search 115/11, 14; 60/221, of the p y j water, ambient water induced 60/222; 114/145 R by the primary jet water, and (3) ambient water captured by the ram action when forward motion is 5 References Cited achieved by the vessel.

UNITED STATES PATENTS The apparatus includes a duct having an inlet means 904,454 11/1908 Rolka .Q 115/11 mam! at a certain distance aft the Primary and 1,375,601 4/1921 Morilt 115/11 x an Outlet with nozzle means to augment in Producing 3,007,305 11/1961 Hamilton 115/14 x the secondaryjet- 3,342,032 9/1967 Cox et a1. 60/221 3,447,324 6/1969 French 115/14 X 7 Chin's 3 Drawing Figures FOREIGN PATENTS OR APPLICATIONS 2,502 0/1868 Great Britain 115/14 l z 3'2 l C I v 30 a; 24 Q 4 14 A? METHOD AND APPARATUS FOR THE RECOVERY OF WATERJET POWER FOR MARINE VESSELS BACKGROUND OF THE INVENTION The present invention is directed to marine vessels of the jet-propelled varietywherein means are utilized to expel a jet of water rearwardly of the vessel. By this invention it is contemplated to provide a secondary inlet and secondary exit nozzle aft ofthe primary nozzle. The secondary inlet is located aft of the primary jet so as to receive a secondary water consisting of a portion of the primary water plus entrained ambient water. The energy content of this secondary water consists of a portion of the entrainment plus ram energy contained in the primary jet in addition to a portion of ram energy resulting from craft motion (if any).

A patent novelty search revealed various concepts having generally similar arrangements; yet, upon a closer review, a substantial difference in construction .as' well as in operation exists.

For instance, the most pertinent U.S. Pat; No. 3,447,324 to French, teaches a primary water jet 32 and a secondary nozzle with a secondary inlet upstream of the primary nozzle, which secondary flow is built up from entrainment by the primary jet flow and the receiving of ram water induced by forward motion. The flow through the secondary inlet being upstream of the primary jet is not induced by the ram action of the primary jet.

Another patent of interest, but less pertinent, appeared to be the French Pat. No. 414,497 to Eidenbenz which discloses a generally similar arrangement to the above-described United States Pat. No. 3,447,324 by French and shows a plurality of concentrically'dispo'sed tubular structures such as indicated at 8 and 9. In addition, US. Pat. No. 3,137,997 by Kaminstein discloses a, hydrojet propulsion arrangement utilizing a secondary nozzle in conjunction with a primary expulsion jet leading from a combustion chamber.

A study of the prior art patents reveals that it is well known a. to create a secondary flow in addition to the primary flow whereby the secondary flow is induced by the primary flow, and

b. to amplify the secondary flow by ram action induced by the forward motion of the marine vessel.

However, the present invention produces a secondary flow which is produced by 1. the ram action of the primary jet;

2. the entrainment action of the primary jet;

3. the ram action of the craft motion, if any.

It is believed that the entrainment water,'which is caused by primary jet water shearing with ambient water and speeding the ambient water by ram and entrainment action into and along with the primary flow portion, produces a significant volume of secondary water flow for the secondary propulsion system described and an attendant improvement in over-all thrust-minus-drag.

Besides the method of producing the abovementioned secondary flow, it appears that the structural embodiment for accomplishing the same is nonexistent in the prior art.

ln the prior art, efficient utilization of propulsion power (high propulsive efficiency) has been achieved through designs which incorporate low-velocity primary jets. However. experience proved that these designs are not generally useful or practical as they are too large, too heavy, and too expensive for applications of waterjet propulsion to high-speed marine vessels.

SUMMARY OF THE INVENTION The present invention is related to a propulsion system for a marine vessel which is characterized by an aft-directed jet or stream of water emerging from a nozzle located next to the hull below the water surface. An opening or secondary inlet, which pierces the underside of the hull some distance aft of the nozzle outlet, captures a quantity of water flow which forms a secondary or auxiliary jet.

The quantity of this captured secondary flow is induced by three separate actions: the first consists of the ram action of the primary jet since it is aimed towards the secondary inlet; a second is the entrainment and shear action of the primary jet as it flows towards the secondary inlet, and the third is the ram action resulting from the forward motion of the marine vessel. The

energy in the captured flow is converted to auxiliary thrust by means of ducting and a secondary nozzle.

This invention is primarily directed toward the improvement of the takeoff performance of waterjetpropelled hydrofoils. However, the concept is general enough to be applicable to any type of water-borne craft.

It is therefore an object of the present invention to produce an increment of net-thrust-minus-drag at a given level of input to the waterjet propulsion means of a marine vessel.

It is another object of the present invention to capture and utilize part of the wasted or residual primary propulsion power. 1

It is still another object of the present invention to capture a portion of volume and energy of the primary jet flow, to entrain ambient water by primary jet action and to capture additional ambient water and energy due to forward motion of the vessel (if any).

It is an additional object to improve theefficiency of waterjet propulsion systems for marine vessels by a most simple and economic method and means.

In general, the present invention improves the netthrust-minus-drag of-a marine vessel that employs a primary waterjet propulsion means, at a given power input, by the 'steps of creating a high kinetic energy region aft of the primary waterjet and retrieving part of the kinetic energy from that region, and thereafter utilizing that retrieved energy as secondary propulsion. The retrieving of the kinetic energy comprises the capturing of a portion of the primary jet flow and a certain amount of ambient water aft of the primary nozzle and forming one combined secondary flow from both captured waters.

A full understanding of the invention and of its further objects and advantages will be had from the following description of an illustrative manner of carrying it out. The particulars of that description, of which the accompanying drawings form a part, are intended only as illustration, and not as a limitation upon the scope of the invention, which is defined in the appended claims.

DESCRIPTION OF THE DRAWINGS FIG. I is a side view of a hydrofoil vessel with a cutaway portion of the primary water propulsion jet and the secondary propulsion jet which encompasses the novel system and preferred embodiment of the present invention.

FIG. 2 is a stern view of the hydrofoil vessel illustrated in FIG. 1 and a typical location of the primary and secondary waterjet exit nozzles.

FIG. 3 is a diagram exemplifying the hydrofoil vessel drag during take-off and the thrust needed to become successfully foil-borne.

DESCRIPTION AND OPERATION OF THE INVENTION As previously mentioned, the present invention relates to improving the propulsion of marine vessels utilizing waterjet propulsion systems. However, in relation 7 to hydrofoil vessels utilizing waterjet propulsion, the present invention improves in addition the take-off mode towards foil-borne travel.

As known, a speedy and smooth take-off for hydrofoil vessels is desirable but difficult to accomplish under all weather conditions since a high thrust/power is required. It is often uneconomic to carry equipment on board for providing such power which is needed only at take-off but not for normal foil-borne cruise modes.

Therefore, since it appears that the present invention offers advantages which are particularly applicable to hydrofoils, the hereinafter explanation, operation and illustration are in connection with hydrofoil vessels.

FIG. 1 illustrates a hydrofoil vessel 10 having a forward strut and foil arrangement 12 and an aft foil and strut arrangement 14 carrying a center water intake means 16. A pump 18 with driving means 20 is mounted aboard the hydrofoil l and connected to the water intake means 16 by a duct 22, for pumping and accelerating the intake water out of the primary jet nozzle 24. The primary water-jet mass 30 diffuses underneath the vessel 10. The diffusion action of the waterjet mass 30 shears and intermeshes with the ambient water 32 and together creates a large kinetic energy loaded water mass.

In addition, a ram water energy 36 due to forward motion of hydrofoil is received which adds to the total energy of the above-mentioned water mass. Inlet 40, which is located downstream of the primary nozzle 24, captures the secondary flow which consists of a portion of the primary jet and a certain amount of ambient water.

Of course, a certain drag is .being experienced by the added structural apparatus, being a duct 42 with jet 44 and inlet 40; however, the total hydrofoil net thrust minus drag is still improved for a given engine input. It is this net thrust improvement that in respect to a hydrofoil 10 will contribute to the necessary thrust at that particular moment where the drag is the highest. For example, in the take-off mode, the hull of the vessel is rising out of the water while at the same time the vessel increases its speed. As illustrated in FIG. 3, the drag increases up to point 50 just prior to the take-off point which is at the moment when the hull surface leaves the water surface and indicated at point 52.

To obtain a thrust augmentation at point 50, which is prior to the true take-off, it is mandatory that the secondary inlet 40 is positioned as low as possible so that air ingestion will not occur to disrupt the thrust augmentation when it is most needed.

For drag reasons, however, it is not desirable to place any propulsion appendages below the hull. Therefore, the lowest point for the secondary inlet should be at the keel of the hydrofoil vessel. Since, in general, multiple secondary nozzles are involved, the positioning is symmetric and above the lowest keel surface while the positioning of the secondary inlet is preferably at the lowest keel so that air-inlet and air ingestion is prevented at the critical take-off point as shown and explained per FIG. 3.

It should be understood, however, that various structural changes or additions to the schematic illustrations can be accomplished, which changes or additions will improve performance in certain instances. For example, the inlet means 40 may be provided with a less or a more projecting means so that less or more water volume is captured. Also, the inlet 40 may be located or formed so as to receive more ambient than direct primary jet water. The primary jet nozzle means could be controlled or set at a specific angle, all of which will produce certain changes.

Accordingly, while there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Now, therefore, I claim:

1. The method of improving the net-thrust-minusdrag of a marine vessel employing a primary waterjet propulsion means at a given power input, comprising the steps of:

a. generating with a primary jet nozzle the action of a primary waterjet which discharges into an unconfined space beneath the keel of said vessel to create an unrestrained high kinetic enrgy region aft of the primary jet,

b. at a point aft of the primary jet initially capturing an amount of ambient water and forming in said unconfined space beneath the vessel a combined flow of the primary waterjet and said ambient water, and

c. directing said combined flow through a secondary jet nozzle to form a secondary waterjet which is discharged into an unconfined space at a point removed from said first-mentioned space.

2. The method of claim 1 including directing said combined flow upwardly through a secondary jet nozzle to form said secondary waterjet which is above said primary waterjet.

3. waterjet propulsion means for marine vessels comprising submerged primary waterjet nozzle means which discharges a waterjet into an unconfined space beneath the hull of said vessel, a duct having an intake section and an exit section, said duct being mounted on said vessel at a predetermined location aft of said submerged primary waterjet nozzle means so that said intake section is adapted to receive a portion of said pri- 6. A take-off thrust augmenting secondary water-jet system for hydrofoil vessels comprising:

a. submerged primary waterjet means which discharges a waterjet into an unconfined space beneath the keel surface of the vessel,

b. a duct having an intake section and an exit section,

said duct being mounted aft of said primary waterjet means such that said intake section is adapted to receive a portion of said primary waterjet and a certain amount of ambient water from said unconfined space,

c. said inlet section being located aft of said primary jet and essentially at said vessels lowest keel surface, and

d said exit section being located above said lowest keel surface aft of said inlet section.

7. A take-off thrust augmenting secondary waterjet system as claimed in claim 6 wherein said inlet section of said duct is located aft of said primary waterjet means at a position which is at least partly within said primary waterjet and wherein said inlet section is structurally flush with said lowest keel surface. 

1. The method of improving the net-thrust-minus-drag of a marine vessel employing a primary waterjet propulsion means at a given power input, comprising the steps of: a. generating with a primary jet nozzle the action of a primary waterjet which discharges into an unconfined space beneath the keel of said vessel to create an unrestrained high kinetic enrgy region aft of the primary jet, b. at a point aft of the primary jet initially capturing an amount of ambient water and forming in said unconfined space beneath the vessel a combined flow of the primary waterjet and said ambient water, and c. directing said combined flow through a secondary jet nozzle to form a secondary waterjet which is discharged into an unconfined space at a point removed from said first-mentioned space.
 2. The method of claim 1 including directing said combined flow upwardly through a secondary jet nozzle to form said secondary waterjet which is above said primary waterjet.
 3. Waterjet propulsion means for marine vessels comprising submerged primary waterjet nozzle means which discharges a waterjet into an unconfined space beneath the hull of said vessel, a duct having an intake section and an exit section, said duct being mounted on said vessel at a predetermined location aft of said submerged primary waterjet nozzle means so that said intake section is adapted to receive a portion of said primary waterjet and a certain amount of ambient water from said unconfined space, and secondary water-jet nozzle means in the exit section of said duct.
 4. The waterjet propulsion means as claimed in claim 3 wherein said inlet section is located aft of said primary waterjet nozzle means and on the same longitudinal axis.
 5. The waterjet propulsion means as claimed in claim 4 wherein said duct exit section is located aft and above said inlet section.
 6. A take-off thrust augmenting secondary water-jet system for hydrofoil vessels comprising: a. submerged primary waterjet means which discharges a waterjet into an unconfined space beneath the keel surface of the vessel, b. a duct having an intake section and an exit section, said duct being mounted aft of said primary waterjet means such that said intake section is adapted to receive a portion of said primary waterjet and a certain amount of ambient water from said unconfined space, c. said inlet section being located aft of said primary jet and essentially at said vessel''s lowest keel surface, and d. said exit section being located above said lowest keel surface aft of said inlet section.
 7. A take-off thrust augmenting secondary waterjet system as claimed in claim 6 wherein said inlet section of said duct is located aft of said primary waterjet means at a position which is at least partly within said primary waterjet and wherein said inlet section is structurally flush with said lowest keel surface. 